1. Field of the Invention
The present invention relates in general to a recording apparatus which performs recording by ejecting, toward a recording medium, mutually different inks respectively from respective nozzle groups.
2. Discussion of Related Art
In a recording apparatus which performs recording by ejecting ink from nozzles, a flushing operation and a purging operation are carried out for maintaining good quality of images to be recorded. In the flushing operation, the ink is ejected to an ink absorption pad for preventing drying of the nozzles. In the purging operation, the ink in which air bubbles and foreign matter are contained is sucked by a suction device, whereby the ink ejection performance is restored. When the purging operation is carried out, the ink which has been sucked from the nozzles may adhere to the nozzle surface. The adhered ink causes the nozzles to be clogged when it is dried, resulting in ink ejection failure. Therefore, the recording apparatus is equipped with a wiping device having a wiping member which wipes the ink adhering to the nozzle surface.
In the recording apparatus, in general, a plurality of inks which are different in color, kind, etc., are used. If the plurality of different inks are wiped by the single wiping member, the inks are mixed with one another. The of different inks, however, causes various undesirable problems described below.
In the recording apparatus arranged to use inks of different colors, for instance, where the inks of the different colors are wiped by the single wiping member, the inks are mixed with each other. If a subsequent wiping operation is carried out with the mixed ink whose color is not originally intended one attaching to and remaining on the wiping member, the mixed ink may enter the nozzles. The mixed ink which has entered the nozzles may be ejected in a subsequent ink ejecting operation.
The recording apparatus is known to use two different kinds of ink, i.e., a dye ink and a pigment ink having respective different characteristics. The dye ink assures good color development and easy tone reproduction of images. The pigment ink does not blur or bleed on plain paper and has high water resistance. If a pigment is used for a black ink, the concentration of the black color can be made high, so that the recorded images become clear or vivid. In view of the above, it is proposed to use the pigment for the black ink and the dye for a yellow ink, a cyan ink, and a magenta ink, for instance.
However, the dye ink and the pigment ink cause aggregation or flocculation reaction upon mixing with each other. For instance, upon the mixing of the pigment ink and the dye ink, the pigment particles in the pigment ink stick to each other or are put together. The sticking of the pigment particles is considered to occur because the negative charge of the pigment particles is cancelled when the positively charged ion present in the dye ink approaches the negatively charged pigment particles. As a result, the dispersed state of the pigment particles is broken. The sticking of the pigment particles is also considered to occur because the dispersed state of the pigment particles is broken due to entering of the solvent as one composition of the dye ink into the pigment ink.
In the recording apparatus arranged to use the dye ink and the pigment ink, therefore, where those different kinds of inks are wiped by the single wiping member, the dye ink and the pigment ink are mixed with each other, resulting in the aggregation reaction. In this case, the nozzles may be clogged with the mixed ink suffering from the aggregation reaction, undesirably causing the ink ejection failure.
The mixing of the inks may further cause solvent solidification, an increase in the viscosity, and so on.
Accordingly, to avoid the miring of the inks, there has been proposed a wiping device having wiping members arranged to respectively wipe the different inks.
One example of such a wiping device will be explained by referring to FIGS. 9–11. FIG. 9 shows relative positional relationship between nozzle rows of a recording head and wiping members in a recording apparatus which has such a wiping device. FIG. 10A is a plan view showing a state in which inks adhere to a nozzle surface and FIG. 10B is a front view of the plan view of FIG. 10A. FIG. 11A is a plan view showing a state in which the wiping members wipe the respective inks and FIG. 11B is a front view of the plan view of FIG. 11A.
The recording apparatus has a recording head comprising a black-ink recording head 300 and a yellow-ink recording head 400 which are adjacent to each other. (The black-ink recording head 300 and the yellow-ink recording head 400 may be hereinafter referred to as “the black-ink head 300” and “the yellow-ink head 400”, respectively.) The black-ink head 300 and the yellow-ink head 400 are arranged to perform recording with a black ink 302 and a yellow ink 402, respectively. The recording apparatus has a nozzle surface which includes a black-ink nozzle surface 303 and a yellow-ink nozzle surface 408 which are adjacent to and flush with each other. (The black-ink nozzle surface 303 and the yellow-ink nozzle surface 403 may be hereinafter simply referred to as “the nozzle surface 303” and “the nozzle surface 403”, respectively.) As shown in FIG. 9, a plurality of black-ink nozzles 301 for ejecting the black ink 302 are formed in rows in the nozzle surface 303 so as to be spaced apart from each other at a predetermined spacing pitch while a plurality of yellow-ink nozzles 401 are formed in rows in the nozzle surface 408 at a predetermined spacing pitch. Namely, a nozzle group consisting of the plurality of black-ink nozzles 301 and a nozzle group consisting of the plurality of yellow-ink nozzles 401 are arranged adjacent to each other such that the rows of the nozzles of the adjacent nozzle groups are parallel to each other.
As shown in FIGS. 10A and 10B, the black ink 302 adheres to the nozzle surface 303 and the yellow ink 402 adheres to the nozzle surface 403. The wiping device includes two wiper blades 200, 201 each provided by an elastic member formed of rubber, for instance. The wiper blades 200, 201 are elongate plates and respectively have wiping surfaces 200a, 201a by which the respective inks are wiped. The wiper blades 200, 201 are positioned such that the wiping surfaces 200a, 210a intersect, at right angles, a moving direction (indicated by arrows F7 in FIG. 10A) in which the wiper blades 200, 201 move. When the recording head stops at a predetermined wiping position, the wiping device operates such that the wiper blades 200, 201 move on the respective nozzle surfaces 303, 403 in the moving direction (F7) while being held in contact with the same 303, 403. As the wiper blades 200, 201 move as described above, the wiper blade 200 wipes the black ink 302 adhering to the nozzle surface 303 and the wiper blade 201 wipes the yellow ink 402 adhering to the nozzle surface 403, as shown in FIG. 11A. The recording apparatus equipped with the wiping device described above is disclosed in JP-A-8-58102, for instance.